Drying system

ABSTRACT

In a drying system using a compression refrigeration system, a condenser is divided into a regulating condenser and a heating condenser. The regulating condenser is capable of regulating the amount of exhaust heat discharged to outside the system. The heating condenser produces moist air by feeding heat to an aqueous object to be dried placed in a processing vessel to evaporate the moisture in the object. Heat of condensation of steam is recovered by an evaporator as heat of a refrigerant, and the recovered heat is discharged in the heating condenser to use it for the vaporization of the moisture in the object, and excess heat is discharged by the regulating condenser to outside the system.

FIELD OF THE INVENTION

The present invention relates to a drying system. More particularly, theinvention relates to a closed drying system using a compressionrefrigeration cycle of high energy efficiency to reduce affect on theenvironment.

DESCRIPTION OF THE PRIOR ART

Sun-drying or air-drying procedures have previously been done. Suchprocedures can dry with high quality, provided that rotting isprevented. However, it is difficult to do such procedures industrially,since vast amount of grounds and long time is required therefor.Further, such procedures are also depending on weather. Whereas,heating-type drying equipment and hot-wind drying equipment energy mustwaste great amount of energy, since hot waste gas including water steammust be drained. Furthermore, vacuum drying equipment, as another dryingprocedure, is still problematic on its operation, operating cost, andthe ease of handling thereof.

Japanese Patent Laid-Open Public Disclosure Hei. 11-63818 (1999)(FIG. 1) discloses vacuum drying equipment. Japanese Patent Laid-OpenPublic Disclosure Hei. 11-197395(1999) (FIG. 1) discloses dryingequipment effectively using energy in which water vapor is condensedthrough an evaporator, and thus obtained low humidity air is reheated(heated again) by a compressor. To their equipment may be added acommercially available, water condenser with reheating properties. Inthis heating method, heat is transferred to an object to be dried fromhot air of low humidity. Therefore, unless the temperature of the objectis lower than that of the hot air and the object is contacted with theair sufficiently, the air of warm, light, and low humidity races betweenthe object and the evaporator, thus extremely decreasing watercondensing efficiency. In conclusion, although the drying equipment isused preferably for drying clothing or woods, which can forcedly bebrought into contact with the air, but not preferably for dryingform-variable objects, for example, from paste into powder.

Although it can easily be thought by those skilled in the art to utilizeheat energy generated through the compression refrigeration cycle asheat for drying object, no the trials for using such heat energy havebeen succeeded because of the following problems.

(1) The capacity of the refrigeration cycle can not be used withpractical efficiency due to the lack of control mechanism for optimizingthe flow rate. The efficiency for condensing water vapor is highlyreduced as the water content of the object is lowered and the relativehumidity of the circulating air is reduced.(2) The refrigeration cycle can not be operated constantly or normally,since the heat balance of the system is not controllable. Otherwise, themechanism required for controlling the heat balance is so complex thatit is difficult to produce the mechanism in a practical cost.(3) Objects can not be assumed with high quality, since the amount ofheat energy used for heating the objects are not controllable.(4) The capacity of the refrigeration cycle can not be used withpractical efficiency due to the lack of the means for enhancing theamount of water vaporized in a unit of time. Although there are thoughta variety of means for facilitating the evaporation, the practicabilitycan not be achieved unless the evaporation capacity suitable for therefrigeration cycle is provided through either one or all of theevaporation facilitator.

DISCLOSURE OF THE INVENTION

Therefore, the object of the present invention is to provide a new anduseful drying system for solving the above mentioned problems bysubstantially reducing amount of energy to be consumed and preventingdischarge waste gas from the system.

The present invention has succeeded to provide a previously impossibledrying system for heating the object through the refrigeration cycle bymaking a variety of countermeasures against the above mentionedproblems.

SUMMARY OF THE INVENTION

The first aspect of the invention is a closed drying system of acompression refrigeration cycle section including a compressor, anevaporator, a condenser, and an expansion valve having being connectedduring a coolant circulating passage, wherein the condenser comprises aheating condenser for supplying heat energy to a moisture-containingobject to generate moisture-laden air, which contains the moisture inwater vapor removed from the object, by evaporation of the moisture ofthe object, and a regulating condenser for exhausting waste heatadjustably out of the system, the evaporator is adapted to remove watervapor from the moisture-laden air by refrigeration, and the coolantcirculating passage delivers coolant from the compressor through theheating condenser into the regulating condenser.

The second aspect of the invention is the drying system according toclaim 1, further comprising; an air-circulator for circulating airbetween the object and the evaporator, a detector for detecting thehumidity and the temperature of the moisture-laden air immediatelybefore flowing over the evaporator, and a flow-rate controller forcontrolling the flow-rate of the moisture-laden air flowing over theevaporator so as to maximize the amount of water to be condensed on thebasis of information obtained by the detector on the humidity and thetemperature.

The third aspect of the invention is the drying system according toclaim 1 or 2, further comprising; another, second coolant supplyingpassage for supplying the coolant directly to the regulating condenser,the second passage being arranged in parallel with the coolant supplyingpassage for supplying the coolant from the compressor to the heatingcondenser, a flow control valve provided in the second coolant supplyingpassage, and wherein the expansion valve is disposed just downstream ofthe regulating condenser.

The fourth aspect of the invention is the drying system according to anyone of the preceding claims, further comprising; a heat-amountcontroller for controlling the amount of heat energy provided by theheating condenser by controlling revolution of the compressor to varythe amount of the coolant to be delivered to the heating condenser.

The fifth aspect of the invention is the drying system according to inany one of the preceding claims, wherein the heat energy is suppliedthrough the bottom of the vessel into the object.

The sixth aspect of the invention is the drying system according to anyone of the preceding claims, further comprising; a stirrer for stirringthe object, and an assistor for assisting the heat transfer, with beingprovided substantially separate from the vessel and the stirrer.

The seventh aspect of the invention is the drying system according toany one of the preceding claims, further comprising; a stirrer forstirring and a pulverizer for pulverizing the object, both beingprovided within the vessel.

The eighth aspect of the invention is the drying system according to anyone of the preceding claims, wherein the object to be charged within thevessel includes a water-containing organic material.

The ninth aspect of the invention is the drying system accordingly toany one of the preceding claims, further comprising; a reheaterconnected directly through the coolant supplying passage to the heatingcondenser and for reheating the air within the vessel, a detector fordetecting the temperature of the coolant within the conduit from thecompressor, and a reheat-amount controller for controlling the amount ofheat energy provided by the reheating element on the basis of theinformation obtained by the detector.

The tenth aspect of the invention is the drying system according to anyone of the preceding claims, wherein the cooling is effected eitherthrough direct cooling mode by flowing the coolant decompressed by theexpansion valve into the evaporator, or through indirect refrigerationmode by circulating the first brine between the evaporator and a coolingelement provided within the vessel and connected heat exchangeably tothe evaporator, and the heating is effected either through directheating mode by flowing the coolant pressurized by the compressor to theheating condenser provided under the bottom of the vessel to heat theobject within the vessel or through indirect heating mode by circulatingthe second brine between the heating condenser and a heater connectedheat exchangeably to the heating condenser and provided under the vesselto heat the object within the vessel.

The 11^(th) aspect of the invention is the drying system according toclaim 10, wherein the indirect cooling mode and the indirect heatingmode are adopted to make it possible to separate the compressionrefrigeration cycle section of the drying system from the processingsection including the vessel.

The 12^(th) aspect of the invention is the processing section includedin the drying system according to claim 11.

The 13^(th) aspect of the invention is the drying system according toclaim 10, wherein the direct or indirect cooling mode and the indirectheating mode are adopted, the vessel includes a vessel body and anair-flow passage both ends of which are separately connected with thevessel body, having the evaporator or the cooling element accommodatedtherein, and the compression refrigeration cycle section and theair-flow passage are assembled separately with the processing sectionexcept for the air-flow passage to compose the drying system.

The 14^(th) aspect of the invention is the processing section includedin the drying system according to claim 13.

In accordance with the drying system of the invention, the amount ofenergy to be consumed would be highly reduced, since the refrigeratingside as well as the heating side of the compression refrigeration cyclecan be used at the same time. Especially, when the amount of heat energydelivered out at the regulating condenser is little, the amount of heatenergy delivered out from the system may also be inhibitedsubstantially. In the compression refrigeration cycle, the refrigeratingcapacity of 3 can normally be obtained from the electric input of 1,although it might vary depending on the operating condition of thesystem. In the heating side forming the heat pump of the system, theheating capacity of 4 (1+3=4) can be obtained. In other words, althoughthe coefficient of performance (COP) of the refrigerating capacity isabout 3, the heating capacity obtained in the heating side can be 4. Inthis connection, the present system using the refrigerating side as wellas the heating side at the same time can utilize the refrigerationcapacity of 3 and the heating capacity of 4 obtained from the electricinput of 1, so that the practical COP of 7 can be achieved. Thus it canbe expected a high energy saving effect.

In the case of prior art rapid high temperature, drying systems such asan electric heater or a gas heater, the surface of the object ishardened or charred, whereas water still remains within the object, andoften the ingredient of the object such as proteins or glucide areaffected by heat. On the other hand, the drying system of the inventionusing the condensing temperature of the refrigeration cycle can operatewith keeping the temperature of the object and the interior of thevessel in ordinary temperature (0-60° C.). Thus the problems of charringor so are prevented. When the condensation pressure of the refrigerationcycle is 2.0 MPa, the condensation temperature of 50° C. is available onR 22, and the condensation temperature of 45.6-50.3° C. is available onR 407.

Further, in accordance with the drying system of the invention, ifincluding the circulator, the stirrer, and pulverizer are additionallyprovided, relatively short time is required for drying the object inordinary temperature, since the evaporation rate of the system broughtinto the maximum due the use of circulators.

Additionally, no odor is released from the system. Taking the fact thatorganic materials often have their particular odors into consideration,the drying system of the invention is especially suitable for organicmaterials of high water content.

In conclusion, the drying system of the invention is referred to as agood system for environment.

The features recited from aspect 2 to the final aspect will provide moreadvantageous effects. These advantages will now be described for eachaspect.

In the drying system of the second aspect, not only the operatingefficiency of the drying system may be enhanced by increasing the totalcondensation amount, but also obtain an object of lower water contentand higher quality by condensing water in the very low temperature nearthe dew point at the end of the drying operation.

In the drying system of the third aspect, the heat balance of thecompression refrigeration cycle can be controlled optimally through theprovision of the second coolant supplying passage.

In the drying system of the fourth aspect, the amount of heat energyprovided by the heating condenser i.e. the amount of heat energysupplied to the object can be controlled.

In the drying system of the fifth aspect, the heat energy generated bythe heating condenser can be efficiently transferred to the object.

In the drying system of the sixth aspect, the heat energy can betransferred to the whole of the object (W) certainly, uniformly, andrapidly by adding the stirrer for stirring and the assister forassisting the heat transfer.

In the drying system of the seventh aspect, the evaporation rate can beincreased by utilizing the stirrer in combination with the pulverizer.Thus the compression refrigeration cycle can be utilized efficiently andthe object of lower water content and higher quality can be obtained.

In the drying system of the ninth aspect, the water removing efficiencycan be enhanced even if the performance of the evaporator is recoveredby the reheating element, whereby in the final drying stage,water-removal efficiency is improved.

In the drying system of any one of the 11^(th) to 14^(th) aspects, thecompression refrigeration cycle section can removably be connected tothe drying section, so that any commercially available ones can be usedas the compression refrigeration cycle section.

BRIEF DESCRIPTION OF THE DRAWINGS

Further feature of the invention will become apparent to those skilledin the art to which the present invention relates from reading thefollowing specification with reference to the accompanying drawings, inwhich:

FIG. 1 is a diagrammatic view illustrating the drying system inaccordance with a first embodiment of the invention;

FIG. 2 is a flow diagram illustrating the cycle of heat transfer of thedrying system of FIG. 1.

FIG. 3 is a block diagram illustrating a control system for controllingthe drying system of FIG. 1;

FIG. 4 is a diagrammatic view generally illustrating the drying systemin accordance with a second embodiment of the invention;

FIG. 5 is a diagrammatic view generally illustrating the drying systemin accordance with a third embodiment of the invention;

FIG. 6 is a diagrammatic view generally illustrating the drying systemin accordance with a fourth embodiment of the invention;

FIG. 7 is a diagrammatic view generally illustrating the drying systemin accordance with a fifth embodiment of the invention;

FIG. 8 is a diagrammatic view generally illustrating the drying systemin accordance with a sixth embodiment of the invention;

FIG. 9 is a diagrammatic view generally illustrating the drying systemin accordance with a seventh embodiment of the invention;

FIG. 10 is a diagrammatic view generally illustrating the drying systemin accordance with an eighth embodiment of the invention;

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The first embodiment of the invention will now be described withreference to FIGS. 1-3.

FIG. 1 is a diagrammatic view illustrating the drying system inaccordance with the first embodiment, FIG. 2 is a flow diagramillustrating the cycle of heat transfer, and FIG. 3 is a block diagramillustrating the system for controlling the drying system of theinvention.

In this embodiment, an object (W) to be dried is tea leaves, whichrepresent moist organic materials.

Essential components of the drying system 1 are compressionrefrigeration cycle section 2 and processing vessel 5. In this dryingsystem 1, the cooling and heating operations are effected on directmodes, respectively.

At first, the arrangement and the operation of the compressionrefrigeration cycle section 2 are described in detail.

The section 2 is provided from the upstream side thereof with acompressor 9, a heating condenser 11, a regulating condenser 13, anexpansion valve 15, and an evaporator 17 in this sequence. A coolant iscirculated within the section through the flow passage 7.

Upon operating the system, the coolant of high temperature and highpressure is delivered from the compressor 9, and then flows through theflow passage 7 into the heating condenser 11. The coolant dischargescondensation heat in the condenser 11. Thus, the object (W) is heatedwhereby water vapor is generated. The coolant is liquefied at theheating condenser 11 and delivered into the regulating condenser 13 andfacilitated liquefaction further therein. The coolant is then deliveredinto the expansion valve 15 and decompressed therethrough to make lowtemperature and low pressure one. Subsequently, the coolant flows intothe evaporator 17. The evaporator 17 is provided within a guide way 18.The guide way 18 is arranged to lead a moisture-laden air into theevaporator 17. After the moisture-laden air, or a high humidity air inthe vessel 5 flows through the guide way 18, the evaporator 17 condensesthe moisture in water vapor contained in the air. That is, when themoisture in the air condensates on the surface of the evaporator 17. Themoisture in water liquid drops on the bottom of the guide way 18, andthen delivered out from the system 1 through drain port (not shown). Thecoolant vaporized within the evaporator 17 is delivered back into thecompressor 9.

The compressor 9 is of a type of variable capacity, so that the capacityof the compressor 9 can be enhanced to increase the flow rate of thecoolant delivered into the heating condenser 11 to increase the amountof heat derived therefrom when the temperature of the object (W) isrelatively low such as upon commencement of the drying system 1. Thusthe efficiency of the system upon commencement can be improved.

The heating condenser 11 is made of a tube of a serpentine pattern ofheat conductive material such as copper. The tube is provided on theouter surface of the bottom of the vessel 5 so as to contact directlytherewith.

The regulating condenser 13 (including an air blower fan 14) is arrangedoutside of the vessel 5. The condenser 13 serves to facilitateliquefaction of the coolant under the effect of outside air temperaturewhen it is difficult to sufficiently cool the coolant due to theincrease in the flow rate of coolant and/or the rising of thetemperature of the object (W). The liquefaction may be effected toprovide the coolant of liquid phase to the expansion valve 15 tostabilize the circulation of the coolant. It is further advantageous tocontrol the temperature of the heating condenser 11 by controlling thecondensing pressure of the compression refrigeration cycle.

FIG. 2 is a flow diagram illustrating the cycle of heat transfer in thedrying system 1. As can be seen therefrom, the heat transfer through theair within the vessel and that through the coolant are illustrated.

FIG. 3 is a block diagram illustrating the system for controlling thedrying system of the invention.

The signals coming from a group of sensors are to be input, as shown inFIG. 3, to the processing section 101 (including CPU, memories, and I/Oports). The power circuit 103 is connected to the processing section 101and the driving circuit 105 for the screw 25 etc. The processing section101 is adapted to process the signals in accordance with the programstored in the memories to control the driving circuit 105 upon energizedby the power circuit 103. The control system comprises the processingsection 101, the power circuit 103, and the driving circuit 105.

The arrangement and the operation of the processing vessel 5 will now bedescribed.

A screw 25 for stirring the object is disposed near the bottom of thevessel 5. The screw 25 includes a motor 26, a shaft 27 connected to themotor 26, and a plurality of blades 29 secured to the shaft 27.

The shaft 27 is arranged in parallel with the bottom of the vessel 5.The blades 29 are secured to the shaft 27 in such an angle that theblades 29 scoop from near the bottom of the vessel 5, the object (W),which has been heated and is likely to easily evaporate the moisture inwater liquid, and the pulverizing members 31, upwardly. The leading edgeof each blade 29 is formed of a soft resinous material and is designedto describe an orbit lapping with the surface of the bottom of thevessel 5.

The pulverizing members 31 include ceramic balls of high hardness. Thepulverizing members 31 are charged within the vessel 5.

The pulverizing members 31 is adapted to be moved in random fashionunder movement of the screw 25, since the pulverizing members 31 is notconnected with the screw 25. The object (W) is pulverized down by thecollision with the pulverizing members 31, thus increasing the surfacearea of thereof capable of being contacted with the moisture-removed airof low humidity to facilitate the discharge of the water vaportherefrom. Additionally, the pulverizing members 31 also serve toenhance thermal transfer, since they are formed of ceramic material ofhigh coefficient of heat transfer.

A blower 33 serves as a circulator for circulating the air within thevessel 5. The blower 33 is arranged to blow downwardly themoisture-removed air from the evaporator 17. Thus, the air circulatingcircuit shown by the blanked arrows is formed upon operating the blower33. In other words, the air within the vessel 15 is circulated betweenthe surface of the object (W) and the evaporator 17. The flow rate ofthe moisture-laden air passing through the evaporator 17 can be adjustedby controlling the operation of the blower 33, i.e. the blower 33 alsoserves as a controller for controlling the capacity of air.

The air derived from the evaporator 17, or the moisture-removed air isof low humidity, which is short of saturation.

A shower 35 is provided above the evaporator 17. The shower 35 disperseswater against the evaporator 17.

The larger the amount of evaporation, the lower the amount ofcondensate, vice versa, i.e. these are the restriction factors with eachother. In other words, the capacity of the drying system 1 can bedetermined by either lower one.

In order to enhance the amount of evaporation, it is advantageous toincrease the amount of evaporation for unit area and to enlarge thesurface area to be contacted with the air of low humidity. The amount ofevaporation for unit area can be increased by (1) reducing moisture, orwater vapor amount in the air, (2) increasing the saturation vaporamount by rising the temperature of the air, and/or (3) increasing thevapor pressure of the object (W). The procedures (1) and (2) can beperformed by re-heating the air. On the other hand, the procedures (1)and (3) can be performed by the method using the system of theinvention. In accordance with the invention, the procedure (1) can beperformed by rapidly changing the moisture-laden air to themoisture-removed air by means of the blower 33. The procedure (3) canalso be performed in accordance with the invention by heating the object(W) and the pulverizing members 31 to increase the pressure of the watervapor within the object (W) and on the surface of the members 31.

Upon rotated the screw 25, the blades 29 are also rotated therewith tostir the object (W) and the pulverizing members 31. Thus, the object (W)placed on the surface of the bottom of the vessel 5 can be scooped outby means of the blades 29 and brought upwardly within the vessel 5,since the orbit described by the leading edge of the blade 29 isdesigned to be lapped with the surface of the bottom of the vessel 5.The heated object (W) is transferred upwardly to facilitate the contactwith the moisture-removed air. On the contrary, another object (W) ofrelatively low temperature is supplied continuously onto the surface ofthe bottom of the vessel 5. Heat transfer to another object (W) from theheating condenser 11 is rapidly performed because another object (W) hasnot yet been heated.

The heat energy of the coolant in the heating condenser 11 istransferred to the bottom of the vessel 5 and then transferred directlyfurther into the object (W) without passing through an air layer. Theheat energy is transferred from the surface of the bottom into theobject (W) steadily, evenly, and rapidly since the screw 25 stirssufficiently the object (W), and the pulverizing members 31 serves as aheat transfer.

Upon operated the screw 25 after the object (W) and the pulverizingmembers 31 are charged into the vessel 5, the object (W) is mashed bythe random rumbling of the members 31 so that the moisture of the object(W) may exude to present on the surface or the vicinity of the material.This is especially useful for increasing the amount of evaporation fromthe object (W).

The pulverizing members 31 are also useful in forming voids between theobjects (W). The exudates, obtained by mashing the object (W) may alsobe transferred on the surface of the members 31. Thus, the moisture ofthe object (W) is easily evaporated from the surface of the members 31and incorporated into the moisture-removed air thereby the air ischanged to the moisture-laden air within the vessel 5. In other words,the members 31 will also bring the effect which can be obtained byincreasing the surface area of the object (W) to be contacted with themoisture-removed air.

Driving the screw 25 in relatively high speed will also bring such anadvantage that chance for contacting the object (W) and the pulverizingmembers 31 with the moisture-removed air is enhanced. However, thusobtained advantage will be diminished when the moisture of the object(W) is substantially decreased and the object (W) is going to transforminto powder. Incidentally, the screw 25 is controlled to reduce thenumber of rotation for preventing the powder from scattering around.

The moisture-removed air being short of saturation is blown on theobject (W) in accordance with the circulation circuit of the air in thevessel.

Thus, the moisture-removed air goes on blowing onto the surface of theobject (W) in according to the circulation passage, so as to achievecontinuous evaporation therefrom.

The moisture of the object (W), already having sufficient heat amount,contacts with the moisture-removed air and evaporate. The evaporatedmoisture or water vapor holds evaporation heat therein as latent heat.When the system 1 is operated under the steady state, the relativehumidity of the moisture-laden air is kept substantially 100% or sountil the drying operation is progressed to reach the predetermineddegree, provided that evaporation of the moisture in water liquid of theobject (W) is facilitated through the mashing and the pulverizingeffects of the screw 25 and the members 31.

The water vapor or the moisture-laden air is transferred to theevaporator 17 in accordance with the circulation passage of the air inthe vessel 5, and then the latent heat is used to condensate the watervapor to water condensates. Thus, the water condensates are deliveredthrough the discharge drain outside of the system 1. Themoisture-removed, low humidity air is again blown on the object (W).

As can be seen From FIG. 1, small circles added on the blanked arrowdesignate the amount of water vapor. In this connection, the arrowdesignating the moisture-removed air just leaving from the evaporator 17has no circles, whereas the following arrows have circles increasingtheir number in the flowing direction. In other words, the moistureamount of the air flowing over the object (W) increases along theflowing direction. Thus formed moisture-laden air is delivered into theevaporator 17, and the moisture is removed upon condensation from themoisture-laden air. That is, the moisture-laden air changes to amoisture-removed air.

The arrangement and the control operation of the detector or sensorsystem will now be described.

The sensor A is adapted to detect the humidity and the temperature ofthe moisture-laden air just before flowing into the evaporator 17. Theair flow of the blower 33 or the flow rate of air passing through theevaporator 17 is adjusted to maximize the amount of condensate based onthe relative humidity, the information on the temperature, and theabsolute humidity obtained by processing the information from the sensorA. This is the most important function of the sensor A.

Since the cooling power is kept constant in the drying system 1, if theflow rate of air through the system is increased gradually, the totalamount of condensates will also increase gradually to the peak, and thendropped rapidly. However, the larger the flow rate of air, the largerthe amount of condensates, if the relative humidity of the airimmediately before condensed is kept 100%. In other words, the amount ofcondensates depends on the flow rate of air i.e. the amount ofcondensates is reduced when the flow rate is too large or too small. Inthis connection, it is necessary to control the flow rate of air so asto maximize the amount of condensate in order to exhaust the capacity ofthe compression refrigeration cycle. The flow rate of air maximizing theamount of condensate depends on the conditions such as the temperatureand/or the humidity of the moisture-laden air, after which will beimmediately condensed. The flow rate of air maximizing the amount ofcondensates is determined by processing these conditions.

During the drying operation through which the object (W) is kept inrelatively water rich condition, the relative humidity of themoisture-laden air is easily kept around 100%, even if the flow rate ofair is high. Therefore, the flow rate determined by working the blower33 is increased in view of maximizing the total amount of condensates.Then the moisture content of the object (W) is reduced as the dryingprocess goes. This will lead to the reduction of the relative humidityof the moisture-laden air, if the flow rate is still high. In order tolower the dew point of the water vapor and sequentially proceed with thecondensation, the flow rate of air in the vessel 5 is reduced gradually.In conclusion, the total amount of condensates is increased. Further,the final stage of the drying operation is performed in extremely lowdew point. Thus, the resultant object (W) has high quality with almostno moisture content.

The revolution rate of the screw 25 is adapted to be controlled on thebasis of the relative humidity and the temperature in the vesselobtained from the sensor A and the absolute humidity calculated byprocessing these information. When the value of the detected relativehumidity is lower than the predetermined one, the revolution of thescrew 25 is increased to facilitate evaporation of the moisture content.When the value of the detected relative humidity is further reducedunder the predetermined lower limit value, the revolution rate of thescrew 25 is rather reduced. This is because the object (W) istransformed into powder as the drying goes, and scattered around if therevolution rate of the screw 25 is still kept high, so that evaporationof the moisture is rather prevented. The final stage of the dryingprocess dries the object (W) with a lot of time, since the process isperformed in the capacity-reduced compressor 9. Even if it is intendedto reduce the moisture content of the object (W) to an extremely lowlevel, the drying system 1 can still be driven efficiently andeconomically by adjusting the capacity of the compressor.

Upon the object (W) is dried further and the absolute humidity of theair in the vessel reached the lower limit value defined in dependence onthe property of the object material, operation of the screw 25 and theblower 33 in the vessel as well as the whole operation of thecompression refrigeration cycle section 2 are stopped. Thus the end ofthe drying process can be determined automatically.

The sensor B is adapted to detect the temperature of the object (W). Thetemperature of the object (W) may be controlled to be the predeterminedvalue by controlling the fan 14 of the regulating condenser 13 inaccordance with the information from the sensor B to vary the amount ofheat to be transferred from the heating condenser 11 to the object (W).In the first embodiment, the heating condenser 11 and the regulatingcondenser 13 are connected in series, so that the condensationtemperature of the compression refrigeration cycle can be varied bycontrolling the fan 14 of the regulating condenser 13. The heattransferred from the heating condenser 11 to the object (W) can thus bevaried.

In the drying system 1, when the operation of the heating condenser 11is not controlled, the temperature of the object (W) increases higherand higher. Thus, the quality of the finished product can not beassured. When the temperature is too high, only the peripheral portionof the object (W) will be dried rapidly and solidified, and the internalportion thereof left as it is. In the worse case, the object (W) willscorched or charred. Although thus produced object (W) containingmoisture inside of the hard scorched surface thereof has a completelydried appearance, it will get moldy and rotted in due course. In otherwords, thus produced object (W) does not have a long term-preferablequality. Further, if the temperature of the object (W) is beyond thatchanging its property, the quality of the object (W) is also spoiled.

In this connection, it is necessary to control the upper limit of thetemperature in accordance with the raw material properties of the object(W) for producing of high quality.

The sensor C detects the temperature of the coolant immediately beforeflowing into the expansion valve 15. The revolution rate of the fan 14of the regulating condenser 13 is adjusted under PID control on thebasis of the temperature information obtained from the sensor C, so thatthe excess amount of heat energy is delivered out of the system 1 tocontrol the condensation temperature of the compression refrigerationcycle to a constant level.

The standard temperature of the coolant before the expansion valve isabout 45° C. (for R 22) or 38° C. (for R 407).

During the normal drying operation, the amount of moisture, which hasbeen evaporated and removed from the object (W), and the amount ofcondensates generated in the evaporator 17, upon condensation of theevaporated moisture, or water vapor are balanced, and the amount oflatent heat transferred, upon the moisture's condensation, into thecoolant is balanced with the amount of heat energy used in evaporationof moisture contained in the object (W) and the pulverizing members 31.Further, although the heat energy generated by the compressor 9 and thescrew 25 is incorporated in the system, the heat energy is dischargedout by the regulating condenser 13.

Upon commencement of the drying system 1, the temperature of the object(W) is relatively low, so that the condensation of the coolant isenhanced, the temperature of the heating condenser is decreased, and theamount of heat energy supplied to the object (W) is decreased. There isno problem in the operation of the compression refrigeration cycle.However, in such a case, it is preferable to increase the revolutionrate of the compressor 9 to increase the flow rate of the coolant. Ifthe compressor 9 is adjusted so, the temperature of the heatingcondenser is also increased so that the temperature rising is improved.Although this can also be performed by controlling the revolution rateof the fan 14 of the regulating condenser 13 to be zero, it is moreeffective to increase the revolution rate of the compressor 9.

The heat energy generated by the screw or so can also contribute thetemperature rising speed of the object (W).

The sensor D detects the temperature of the coolant at the inflow sideof the evaporator 17, and the sensor E detects the temperature of thecoolant at the outflow side of the evaporator 17. When the temperaturedifference between those measured at the sensor E and D is smaller thanthe predetermined value, the evaporator 17 is regarded to be in themalfunction condition due to icing etc., so that the defrostingoperation is effected. The defrosting operation is performed by stoppingthe operation of the compressor 9 and/or spraying water from the shower35 onto the evaporator 17 and/or the full power operation of the blower.

The drying system 41 in accordance with the second embodiment will nowbe described with reference to FIG. 4. This figure is a diagrammaticview generally illustrating the drying system 41. The structuralcomponents of the drying system 41 illustrated in FIG. 4 are designatedby the same reference numeral as those used in FIG. 1, provided thatthose corresponding components are substantially identical with eachother. In this connection, the description is omitted on thecorresponding components.

The drying system 41 is provided with the first flow passage (coolantcirculating passage 7) for delivering coolant from the compressor 9 tothe heating condenser 11, and the second flow passage (by-pass passage)43 in parallel with the first one for delivering coolant directly intothe regulating condenser 13. The second flow passage is provided with aflow control valve 45. When it is almost unnecessary to increase thetemperature of the object (W), the divergence of the flow control valve45 is increased to deliver the majority of the coolant from thecompressor 9 to the regulating condenser 13, so that the amount of heatenergy to be provided by the heating condenser 11 is reduced to suppressthe temperature rise of the object (W).

The sensor F detects the temperature of the coolant delivered from thecompressor 9. The divergence of the flow control valve 45 may becontrolled on the basis of the information on the temperature obtainedfrom the sensor F.

The drying system 51 of the third embodiment will now be described withreference to FIG. 5.

FIG. 5 is a diagrammatic view generally illustrating the drying system51. The structural components of the drying system 51 illustrated inFIG. 5 are designated by the same reference numeral as those used inFIG. 1, provided that those corresponding components are substantiallyidentical with each other. In this connection, the description isomitted on the corresponding components.

The principal aspect of the drying system 51 is a reheating section 52.The coolant of high temperature and high pressure flows from thecompressor 9 through the flow passage 7 and into the heating condenser11 to provide heat energy to the object (W) through liquefying thecoolant. The reheating section 52 connected in series with the heatingcondenser 11 includes a reheating element 55 for heating air immediatelyafter passing through the evaporator 17. The amount of heat energy to besupplied by the reheating element 55 is controlled by the flow controlvalves 54 and 56 provided on a coolant supplying passage 53. The inflowconduit from the compressor 9 is provided with the temperature sensor F.

The reheating element 55 is a fin plate heat exchanger served as acondenser. The method for using this heat exchanger will now bedescribed. At first, the flow control valve 54 is closed completely,whereas the flow control valves 56 is opened. The object (W) in thevessel 5 includes very large amount of moisture at the beginning of thedrying process. Upon operating the compression refrigeration cycle, thewater liquid is heated by the heating condenser 11 and large amount ofwater vapor is generated within the vessel 5. The heating temperature ofthe heating condenser 11 is controlled by adjusting the amount of heatenergy delivered out of the system through controlling the operation ofthe fan 14 of the regulating condenser 13.

When it is intended to heat the object (W) rapidly, the fan 14 of theregulating condenser 13 is stopped to provide whole heat energygenerated through the operation of the compression refrigeration cyclefrom the heating condenser 11 to the object (W) within the vessel 5. Theobject (W) is dried by cooling the air in the vessel 5 including largeamount of water vapor at the evaporator 17 to make water liquid. Asdescribed above, the system is operated in high efficiency, since wholeheat energy of the system is available. Thus the energy efficiencydesignated by COP will reach to 7.

When the object (W) is sufficiently dried and the emission of moistureis decreased, the humidity of the air in the vessel 5 is also reduced.Thus the amount of moisture removed from the moisture-laden air at theevaporator 17 is reduced and the lower pressure of the coolant flowinginto the compressor 9 is dropped.

This reduction of the lower pressure will bring the lowering of thetemperature of the coolant from the compressor 9. The timing of thelowering of the temperature is detected by the information on thetemperature from the sensor F.

In this situation, the temperature within the vessel 5 is not raisedeven by providing the heat energy through the heating condenser 11. Thenthe flow control valve 54 is opened to deliver coolant into thereheating element 55 to rise the temperature of the outflow side of theevaporator 17. Thus the temperature of the vessel 5 is also increased torecover the lower pressure of the compression refrigeration cycle andthe performance of the evaporator 17. In this connection, it is expectedthat the dryness of the object (W) can also be increased further.

In the above mentioned third embodiment, the relative humidity sensor Ais not necessary be provided, since whether the reheating section 52 isto be operated or not can be determined on the control signal from thesensor F. This is because the operating condition of the compressionrefrigeration cycle can be detected on the basis of the relativehumidity within the vessel 5.

The fourth embodiment of the present invention will now be describedwith reference to FIG. 6.

FIG. 6 is a diagrammatic view generally illustrating the drying system61. The structural components of the drying system 61 illustrated inFIG. 6 are designated by the same reference numeral as those used inFIG. 1, provided that those corresponding components are substantiallyidentical with each other. In this connection, the description isomitted on the corresponding.

In this drying system, the indirect cooling and heating mode is adopted.

The first brine circulating circuit 67 includes a refrigerator 69 and acirculating pump 72. The refrigerator 69 is provided within the vessel5. The first brine circulating circuit 67 is connected to the evaporator65 of the compression refrigeration cycle section so as to be able toexchange the heat energy. Thus the indirect refrigerating section 63 isformed. The heat exchanger for the first brine as well as the coolant ispreferably of the serviceable compact plate type. Upon being driven thecirculating pump 72, the first brine, which has been cooled at theevaporator 65 flows into the refrigerator 69 for cooling anddehumidifying the moisture-laden air which will flow through the guideway 18.

The second brine circulating circuit 75 includes a heater 77 andcirculating pump 78. The heater 77 is provided on the outer surface ofthe bottom of the vessel 5. The second brine circulating circuit 75 isconnected to the heating condenser 74 of the compression refrigerationcycle section so as to be able to exchange the heat energy. Thus theindirect refrigerating section 73 is formed. The heat exchanger for thesecond brine as well as the coolant is preferably of the serviceablecompact plate type as with the evaporator 65. Upon being driven thecirculating pump 78, the second brine, which has been heated at theheating condenser 74, flows into the heater 77 to increase thetemperature of the object (W) to change the moisture from water liquidto water vapor form.

The first and second brine circuits are independent of each other, sothat the first and second brines may be the same or the differentmaterials. The brine utilized herein includes warm water and cold water.

The indirect refrigerating section 63 and the indirect heating section73 forms a processing section together with the vessel 5 and theequipment disposed within the vessel 5. The compression refrigerationcycle section 81 including the compressor 9, the evaporator 65, theheating condenser 74, and the expansion valve 15 connected each otherthrough the coolant circulating passage is detached with the first andsecond brine circulating circuits 67 and 75.

The control unit 107 is provided only on the compression refrigerationcycle section 81.

Following advantages can be obtained by detachably connecting theprocessing section to the compression refrigeration cycle section 81.

(1) The manufacture and the maintenance of these sections can beeffected separately.

When the evaporator 65 is disposed within the vessel, it is difficult tomake maintenance thereon, in spite of the corrosive property thereof.However, such disadvantage is avoided in this arrangement;

(2) The compression refrigeration cycle section 81 is fitted toapparatus of various designs by standardizing the connecting portions(the evaporator 65 and the heating condenser 74). Thus, the utility ofthe compression refrigeration cycle section 81 can be enhanced and thecost for manufacturing the same can be reduced.(3) The driving circuit 105 is controlled on the basis of theinformation detected in the compression refrigeration cycle section 81so that the confirmation of the operation and the maintenance of thedrying system 61 is made easily.

The fifth embodiment of the present invention will now be described withreference to FIG. 7.

FIG. 7 is a diagrammatic view generally illustrating the drying system83. The structural components of the drying system 83 illustrated inFIG. 7 are designated by the same reference numeral as those used inFIG. 6, provided that those corresponding components are substantiallyidentical with each other. In this connection, the description isomitted on the corresponding components.

In this drying system 83, the reheating section 84 is provided.

The reference numeral 85 is added to a branch passage. The passage 85 isconnected at both ends thereof to the second brine circulating circuit75 downstream of the heater 77. The reheating element 87 is disposedwithin the vessel 5. The passage 85 is also provided with a circulatingpump 88 for forcing the brine into the reheating element 87. In such anarrangement, the system increases the amount of water to be removed fromthe object (W), as with the system of the third embodiment. In thisconnection, the dryness of the object (W) is expectedly increased. Thecompression refrigeration cycle section 81 has an arrangement which canbe detached from the drying system 83 as with the fourth embodimentshown in FIG. 6, so that the above mentioned advantages (1), (2), and(3) are also obtained in this embodiment.

The sixth embodiment of the present invention will now be described withreference to FIG. 8.

FIG. 8 is a diagrammatic view generally illustrating the drying system91. The structural components of the drying system 91 illustrated inFIG. 8 are designated by the same reference numeral as those used inFIG. 1, provided that those corresponding components are substantiallyidentical with each other. In this connection, the description isomitted on the corresponding components.

In the drying system 91, the wall 95 of the vessel body 93 is of hollowstructure made of the same material as that employed in the heatingcondenser 11. The vessel body 93 is adapted to be closed by lid 97. Thereference numeral 99 is added to the flow passages. The intermediateportion of the passage extends laterally, and both side portions extenddownwardly to the lid 97. The evaporator 17 is provided within thepassage.

Although the screw 25 is of vertical type, the structure thereof issubstantially the same as that used in the drying system 1.

The reference numeral 100 is added to the blower for circulating the airin the direction designated by blanked arrows. No pulverizing materials31 are charged into the vessel body 93.

The object (W) is heated by coolant delivered into the wall 95 of thevessel body 93 from the compressor 9. The coolant leaving the wall 95 isdelivered into regulating condenser 13, and decompressed by means ofexpansion valve 15, then flows into the evaporator 17.

In this drying system 91, the area in which the moisture-laden air isproduced (within the vessel body 93) and the area in which themoisture-removed air is generated (near the evaporator 17) are separatedfrom each other by the flow passages 99, so that the transformation fromthe moisture-laden air to the moisture-removed air vice versa are doneefficiently.

The seventh embodiment of the present invention will now be describedwith reference to FIG. 9.

FIG. 9 is a diagrammatic view generally illustrating the drying system104 obtained by retrofitting the drying system 91 (FIG. 8) to adopt theindirect cooling and/or heating system of the drying system 61 (FIG. 6).The structural components of the drying system 104 illustrated in FIG. 9are designated by the same reference numeral as those used in FIGS. 8and 6, provided that those corresponding components are substantiallyidentical with each other. In this connection, the description isomitted on the corresponding components.

A pair of air-flow passages is connected to the lid 97. One end of eachpassage is connected to the lid, and the other end of the passage isprovided with a flange 101. These flanges are adapted to be connected tothe flanges 102 provided at the both ends of the flow passage 99. Whenthese flanges 101 and 102 are connected, the flow passage of the systemis defined.

As can be seen from the above, the air flow passages 98 and 99 can bedetached from each other, so that the vessel body 93 is separatelyassembled from the main structure of the system including thecompression refrigeration cycle section 81, the air flow passage 99, andthe refrigerator 69.

The eighth embodiment of the present invention will now be describedwith reference to FIG. 10.

FIG. 10 is a diagrammatic view generally illustrating the drying system105 obtained by retrofitting the drying system 104 (FIG. 9) to adopt thedirect cooling system of the drying system 91 (FIG. 8). The structuralcomponents of the drying system 105 illustrated in FIG. 10 aredesignated by the same reference numeral as those used in FIGS. 9 and 8,provided that those corresponding components are substantially identicalwith each other. In this connection, the description is omitted on thecorresponding components.

While particular embodiments of the present invention have beenillustrated and described, it should be obvious to those skilled in theart that various changes and modifications can be made without departingfrom the spirit and scope of the invention.

The compressor may for example be of a type of fixed displacement. Insuch a case, the capacity of the compressor may be adjusted by theintermittent (on/off) operation. This is suitable for the relativelysmaller vessel, or for the case in which the final water content of theobject is not relatively low.

The flow control valve may be an electromagnetic valve of on/off type.In such a case, the amount of heat energy can be adjusted by theintermittent (on/off) operation thereof.

The coefficient of heat transfer of the pulverizing assisting materials31 may preferably be as high as possible. The examples of such materialinclude metal or ceramics. Wooden materials are not preferable. Bamboois better than the wooden materials.

It is a matter of course that the object (W) is not limited to organicmaterials.

The drying system of the present invention can be used under vacuum. Insuch a case, the vessel is designed to withstand the vacuum within thevessel. The system operates by pumps or blowers of relatively lowpressure or ejector. Provided that the vacuum source is connected to thedrain port to deliver the condensed water out of the system, the vacuumsource must be selected to be able to handle the water without anyproblem.

The design of the drying system of the second embodiment can be changedto control the flow rate of the coolant delivered into the reheatingelement by means of the electromagnetic valve of on/off type. Further,the reheating element for heating the air in the vessel can be aradiator of on/off type.

INDUSTRIAL APPLICABILITY

In accordance with the drying system of the invention, the amount ofenergy to be consumed can be reduced substantially. In other words, thedrying system of the invention is good for the natural environment andalso is economically advantageous.

In the arrangement in which the compression refrigeration cycle sectionincluding a control unit can be detached from the vessel, the onerefrigeration cycle section can advantageously be used in the variety ofvessels. Thus the mass production of the compression refrigeration cyclesection can be performed.

1. A closed drying system, comprising: a vessel that includes amoisture-containing object and an air circulator; and a compressionrefrigeration cycle section that includes: a compressor; a heatingcondenser that supplies heat energy to the object through a bottom ofthe vessel to generate moisture-laden air, which contains moisture inwater vapor removed from the object, by evaporation of the moisture ofthe object; a regulating condenser that adjustably exhausts waste heatout of the system; an evaporator that is located inside the vessel andremoves the water vapor from the moisture-laden air by refrigeration; anexpansion valve connected after a circulating passage that deliverscoolant from the compressor through the heating condenser to theregulating condenser; and a sensor that detects a temperature of coolantimmediately before the expansion valve, from which temperatureinformation the regulating condenser keeps a coolant temperature beforethe expansion valve at a constant level, wherein the air circulatorcirculates air between the object and the evaporator within the vesselwhereby moisture-removed air with latent heat removed will contact withthe object.
 2. The closed drying system according to claim 1, furthercomprising; a detector that detects humidity and temperature of themoisture-laden air immediately before flowing over the evaporator, and aflow-rate controller that controls the flow-rate of the moisture-ladenair flowing over the evaporator so as to maximize an amount of water tobe condensed on the basis of information obtained by the detector on thehumidity and the temperature.
 3. The closed drying system according toclaim 1, further comprising; a second coolant supplying passage thatsupplies the coolant directly to the regulating condenser, the secondcoolant supplying passage being arranged in parallel with the coolantsupplying passage that supplies the coolant from the compressor to theheating condenser, a flow control valve provided in the second coolantsupplying passage, and a sensor that detects a temperature of thecoolant flowing out from the compressor, whereby the divergence of aflow control valve is controlled based on the temperature informationfrom the sensor, wherein the expansion valve is disposed just downstreamof the regulating condenser.
 4. The closed drying system according toclaim 1, further comprising; a heat-amount controller that controls anamount of heat energy provided by the heating condenser by controllingrevolution of the compressor to vary an amount of the coolant to bedelivered to the heating condenser.
 5. The closed drying systemaccording to claim 1, further comprising; a stirrer provided within thevessel that stirs the object.
 6. The closed drying system according toclaim 1, further comprising; a stirrer that stirs, and a pulverizer thatpulverizes the object, both being provided within the vessel.
 7. Theclosed drying system according to claim 1, wherein the object to becharged within the vessel includes a water-containing organic material.8. The closed drying system accordingly claim 1, further comprising; areheater connected directly through the coolant circulating passage tothe heating condenser and that reheats the air within the vessel, adetector that detects a temperature of the coolant within a conduit fromthe compressor, and a reheat-amount controller that controls an amountof heat energy provided by the reheater on the basis of the temperaturedetected by the detector.
 9. The closed drying system according to claim1, wherein cooling is effected either through direct cooling mode byflowing the coolant decompressed by the expansion valve into theevaporator, or through indirect refrigeration mode by circulating afirst brine between the evaporator and a cooling element provided withinthe vessel and connected heat exchangeably to the evaporator, and aheating is effected either through direct heating mode by flowing thecoolant pressurized by the compressor to the heating condenser providedunder the bottom of the vessel to heat the object within the vessel orthrough indirect heating mode by circulating a second brine between theheating condenser and a heater connected heat exchangeably to theheating condenser and provided under the vessel to heat the objectwithin the vessel.
 10. The closed drying system according to claim 9,wherein the indirect cooling mode and the indirect heating mode areadopted to make it possible to separate a compression refrigerationcycle section of the closed drying system from a processing sectionincluding the vessel.
 11. The processing section included in the closeddrying system according to claim
 10. 12. The closed drying systemaccording to claim 9, wherein the direct or indirect cooling mode andthe indirect heating mode are adopted, the vessel includes a vessel bodyand an air-flow passage both ends of which are separately connected withthe vessel body, having the evaporator or the cooling elementaccommodated therein, and the compression refrigeration cycle sectionand the air-flow passage are assembled separately with the processingsection except for the air-flow passage to compose the closed dryingsystem.
 13. The processing section included in the closed drying systemaccording to claim
 12. 14. The closed drying system according to claim1, wherein the coolant in the compression refrigeration cycle section isseparate from air circulated in the vessel by the air circulator.